Min and Max in Custom Query in Spring Boot JPA

On the Eclipse, create a Spring Boot project

Enter Project Information:

Name: SpringBootDataJPA
Group: com.demo
Artifact: SpringBootDataJPA
Description: Spring Boot Data JPA
Package: com.demo

Select the technologies and libraries to be used:

JPA
MySQL

Click Next button to show Site Information for project

Click Finish button to finish create Spring Boot project

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.2.0.M1</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.demo</groupId>
	<artifactId>SpringBootDataJPA</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>SpringBootDataJPA</name>
	<description>Spring Boot Data JPA</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<scope>runtime</scope>
		</dependency>

		<dependency>
			<groupId>net.bytebuddy</groupId>
			<artifactId>byte-buddy</artifactId>
			<version>1.9.12</version>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

	<repositories>
		<repository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</repository>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
		</repository>
	</repositories>
	<pluginRepositories>
		<pluginRepository>
			<id>spring-snapshots</id>
			<name>Spring Snapshots</name>
			<url>https://repo.spring.io/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</pluginRepository>
		<pluginRepository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
		</pluginRepository>
	</pluginRepositories>

</project>

Create a database with the name is springbootdatajpa. This database have a table: Product

--
-- Table structure for table `product`
--

CREATE TABLE `product` (
  `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
  `name` varchar(250) COLLATE utf8_unicode_ci NOT NULL,
  `price` decimal(10,1) NOT NULL,
  `quantity` int(11) NOT NULL,
  `description` text COLLATE utf8_unicode_ci NOT NULL,
  `photo` varchar(250) COLLATE utf8_unicode_ci NOT NULL,
  `featured` tinyint(1) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

--
-- Dumping data for table `product`
--

INSERT INTO `product` (`name`, `price`, `quantity`, `description`, `photo`, `featured`) VALUES('Mobile 1', '2.0', 2, 'description 1', 'thumb1.gif', 0);
INSERT INTO `product` (`name`, `price`, `quantity`, `description`, `photo`, `featured`) VALUES('Mobile 2', '1.0', 5, 'description 2', 'thumb2.gif', 1);
INSERT INTO `product` (`name`, `price`, `quantity`, `description`, `photo`, `featured`) VALUES('Mobile 3', '3.0', 9, 'description 3', 'thumb3.gif', 0);
INSERT INTO `product` (`name`, `price`, `quantity`, `description`, `photo`, `featured`) VALUES('Computer 1', '5.0', 12, 'description 4', 'thumb1.gif', 1);
INSERT INTO `product` (`name`, `price`, `quantity`, `description`, `photo`, `featured`) VALUES('Computer 2', '7.0', 5, 'description 5', 'thumb1.gif', 0);
INSERT INTO `product` (`name`, `price`, `quantity`, `description`, `photo`, `featured`) VALUES('Computer 3', '12.0', 2, 'description 6', 'thumb2.gif', 1);
INSERT INTO `product` (`name`, `price`, `quantity`, `description`, `photo`, `featured`) VALUES('Laptop 1', '3.0', 8, 'description 7', 'thumb2.gif', 0);
INSERT INTO `product` (`name`, `price`, `quantity`, `description`, `photo`, `featured`) VALUES('Laptop 2', '4.0', 11, 'description 8', 'thumb3.gif', 1);
INSERT INTO `product` (`name`, `price`, `quantity`, `description`, `photo`, `featured`) VALUES('Laptop 3', '2.0', 15, 'description 9', 'thumb2.gif', 0);

Open application.properties file in src/main/resources folder and add configurations connect to database as below:

spring.datasource.url= jdbc:mysql://localhost:3306/springbootdatajpa
spring.datasource.username=root
spring.datasource.password=123456

Create new package named com.demo.entities. In this package, create new java class named Product.java as below:

package com.demo.entities;

import java.io.Serializable;

import java.math.BigDecimal;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "product")
public class Product implements Serializable {
	private static final long serialVersionUID = 1L;

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private int id;

	private String name;

	private BigDecimal price;

	private int quantity;

	private String description;

	private String photo;

	private boolean featured;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public BigDecimal getPrice() {
		return price;
	}

	public void setPrice(BigDecimal price) {
		this.price = price;
	}

	public int getQuantity() {
		return quantity;
	}

	public void setQuantity(int quantity) {
		this.quantity = quantity;
	}

	public String getDescription() {
		return description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	public String getPhoto() {
		return photo;
	}

	public void setPhoto(String photo) {
		this.photo = photo;
	}

	public boolean isFeatured() {
		return featured;
	}

	public void setFeatured(boolean featured) {
		this.featured = featured;
	}

}

Create new package named com.demo.repositories. In this package, create new interface named ProductRepository.java implement from CrudRepository interface of Spring Framework as below:

package com.demo.repositories;

import java.math.BigDecimal;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
import com.demo.entities.Product;

@Repository("productRepository")
public interface ProductRepository extends CrudRepository<Product, Integer> {

	@Query(value = "SELECT min(price) FROM Product")
	public BigDecimal min();

	@Query(value = "SELECT max(price) FROM Product")
	public BigDecimal max();

}

Create new package named com.demo.services. In this package create new interface named ProductService.java as below:

package com.demo.services;

import java.math.BigDecimal;

public interface ProductService {

	public BigDecimal min();

	public BigDecimal max();

}

In com.demo.services package, create new java class named ProductServiceImpl.java implement from ProductService interface

package com.demo.services;

import java.math.BigDecimal;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.demo.repositories.ProductRepository;

@Transactional
@Service("productService")
public class ProductServiceImpl implements ProductService {

	@Autowired
	private ProductRepository productRepository;

	@Override
	public BigDecimal min() {
		return productRepository.min();
	}

	@Override
	public BigDecimal max() {
		return productRepository.max();
	}

}

In com.demo package, create new java class named JPAConfiguration.java as below:

package com.demo;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import com.demo.services.ProductService;
import com.demo.services.ProductServiceImpl;

@Configuration
@EnableAutoConfiguration
@EnableTransactionManagement
@EnableJpaRepositories(basePackages = { "com.demo.repositories" })
@ComponentScan("com.demo")
@PropertySource("classpath:application.properties")
public class JPAConfiguration {

	@Bean
	public ProductService productService() {
		return new ProductServiceImpl();
	}

}

Create new package named com.demo.main. In this package, create new java file named Demo.java as below:

package com.demo.main;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;

import com.demo.JPAConfiguration;
import com.demo.services.ProductService;

public class Demo {

	public static void main(String[] args) {
		try {
			AbstractApplicationContext context = new AnnotationConfigApplicationContext(JPAConfiguration.class);
			ProductService productService = context.getBean(ProductService.class);
			System.out.println("The biggest price: " + productService.max());
			System.out.println("The smallest price: " + productService.min());
			context.close();
		} catch (Exception e) {
			System.out.println(e.getMessage());
		}
	}

}

The biggest price: 12.0
The smallest price: 1.0

Create Spring Boot Project

Configure pom.xml

Create Database

Structure of Product Table

Data of Product Table

Database Configuration

Entities Class

ProductRepository Interface

ProductService Interface

ProductServiceImpl Class

JPA Configuration

Project Structure

Application

Output